nft-qos: support mac address based speed limit

This patch makes it possible to configure and limit per-client internet
speed based on MAC address and it can work with SQM.
This feature is what OpenWRT currently lacks. This patch is largely based
on static.sh and the configuration file is similar to original nft-qos.

New configuration options and examples are listed below

config default 'default'
    option limit_mac_enable '1'
config client
	option drunit 'kbytes'
	option urunit 'kbytes'
	option hostname 'tv-box'
	option macaddr 'AB:CD:EF:01:23:45'
	option drate '1000'
	option urate '50'
config client
	option drunit 'kbytes'
	option urunit 'kbytes'
	option hostname 'my-pc'
	option macaddr 'AB:CD:EF:01:23:46'
	option drate '3000'
	option urate '2000'

limit_mac_enable - enable rate limit based on MAC address
drunit - download rate unit
urunit - upload rate unit
macaddr - client MAC address
drate - download rate
urate - upload rate

Signed-off-by: Tong Zhang <ztong0001@gmail.com>

net/nft-qos/files/nft-qos.init

@@ -7,6 +7,7 @@
 . /lib/nft-qos/monitor.sh
 . /lib/nft-qos/dynamic.sh
 . /lib/nft-qos/static.sh
+. /lib/nft-qos/mac.sh
 . /lib/nft-qos/priority.sh
 
 START=99
@@ -19,6 +20,7 @@ service_triggers() {
 	qosdef_validate_dynamic
 	qosdef_validate_static
 	qosdef_validate_priority
+	qosdef_validate_mac
 	procd_close_validate
 }
 
@@ -26,6 +28,7 @@ start_service() {
 	config_load nft-qos
 
 	qosdef_init_env
+	qosdef_flush_mac
 	qosdef_flush_static
 	qosdef_flush_dynamic
 	qosdef_remove_priority
@@ -34,6 +37,7 @@ start_service() {
 	qosdef_init_monitor
 	qosdef_validate_dynamic default qosdef_init_dynamic
 	qosdef_validate_static default qosdef_init_static
+	qosdef_validate_mac default qosdef_init_mac
 	qosdef_validate_priority default qosdef_init_priority
 	qosdef_init_done
 	qosdef_start
@@ -42,6 +46,7 @@ start_service() {
 stop_service() {
 	qosdef_flush_dynamic
 	qosdef_flush_static
+	qosdef_flush_mac
 	qosdef_remove_priority
 	qosdef_clean_cache
 }